In Swift, the Proxy Design Pattern can be implemented by creating a class that acts as the proxy. This class should have the same interface as the original object, but it should also have the additional functionality that is needed. For example, if the original object is a heavy resource that takes a long time to load, the proxy class could provide a method for lazy loading the object only when it is needed.
Here is an example of how the Proxy Design Pattern can be implemented in Swift:
The ImageProxy class has a private realImage property that holds the instance of RealImage that it represents. This property is initialized as nil to represent the fact that the real image has not yet been loaded.
The display() method of ImageProxy checks if the realImage property is nil, and if it is, it creates an instance of RealImage and assigns it to the realImage property. This is the lazy loading functionality of the proxy, as it only loads the real image when it is needed. Once the real image is loaded, the display() method simply calls the display() method of the RealImage instance to display the image.
The ImageProxy class also has a imageName property that holds the name of the image file that it represents. This property is used to create the RealImage instance when it is needed.
This is just one example of how the Proxy Design Pattern can be implemented in Swift. The pattern can be adapted and extended to suit the specific needs of any project.